Taken from www.bad.org.uk

Keratoacanthoma

What are the aims of this leaflet?

This leaflet has been written to help you understand more about keratoacanthomas (KAs). It tells you what they are, what causes them, what can be done about them, and where you can find out more about them.

What are keratoacanthomas?

KAs are relatively common benign skin growths from the cells surrounding the hair unit that usually appear in sun exposed skin. Clinically they can’t be easily differentiated from a more serious skin cancer, a squamous cell carcinoma (SCC). KAs grow quickly over the first few weeks but do not spread to other parts of the body. If left alone, they will usually go away by themselves in 4 to 6 months.

What causes keratoacanthomas?

Their precise cause is not known. Factors that may play a part include heavy sun exposure, contact with some chemicals, smoking, infection with some strains of wart virus, a suppressed immune system, and minor injuries to the skin.

KAs are more common in fair than in dark-skinned individuals, and more so in men than in women. They are rare under the age of 20 and become more common with age.

Are keratoacanthomas hereditary?

Usually not, although multiple KAs are a part of a few rare inherited conditions.

What are the symptoms of a keratoacanthoma?

Usually there are none apart from their cosmetic appearance, as they tend to be on exposed skin.

What does a keratoacanthoma look like?

KAs occur more frequently on the face, and less often on the backs of the hands and forearms. Usually they are solitary and surrounded by normal skin.

The first sign is a small, round, skin-coloured or red bump, looking like a spot but without pus. As it grows, a KA takes on its characteristic appearance. The small bump becomes firm, raised and dome-shaped with a smooth surface and a central plug made of brown keratin (the material of which hair and the outermost layer of skin is made). If the plug comes out, a crater will remain, giving the KA the appearance of a ‘mini-volcano’. As a KA heals, it flattens, eventually leaving only a puckered scar.

KAs pass through three stages each lasting 2 to 3 months. Initially there is a rapid growth phase, followed by a static phase when it remains unchanged, and then a phase of healing.

How will a keratoacanthoma be diagnosed?

The most important condition to rule out is one type of skin cancer called a squamous cell carcinoma. For this reason, it is likely that a KA will be cut out and examined under the microscope.

Can a keratoacanthoma be cured?

Yes, removal leads to cure.

How can a keratoacanthoma be treated?

If left alone, KAs will eventually go away spontaneously without any treatment; however, this can take many months.

One method of removal is to scrape the KA off with a sharp, spoon-like instrument (a curette) under a local anaesthetic, and then to cauterize the raw area left behind. The specimen that has been scraped off can then be sent for microscopic examination.

If there is any concern about the diagnosis, it is best for the lesion to be cut out and the area closed with stitches; this provides a better specimen for microscopic examination.

Occasionally, small KAs can be dealt with by freezing them with liquid nitrogen.

Self care (What can I do?)

If you have had a KA, it is advisable that you examine your own skin regularly. Avoiding too much exposure to the sun is sensible. You can achieve this by covering yourself up and using sunscreen; use a high factor (minimum sun protection factor 30), broad spectrum sunscreen (blocks both types of ultraviolet radiation, UVA and UVB) on areas that you cannot cover.

Where can I get more information about keratoacanthomas?

Web links to detailed leaflets:

www.dermnetnz.org/lesions/keratoacanthoma.html

For details of source materials used please contact the Clinical Standards Unit (clinicalstandards@bad.org.uk).

This leaflet aims to provide accurate information about the subject and is a consensus of the views held by representatives of the British Association of Dermatologists: its contents, however, may occasionally differ from the advice given to you by your doctor.

This leaflet has been assessed for readability by the British Association of Dermatologists’ Patient Information Lay Review Panel

BRITISH ASSOCIATION OF DERMATOLOGISTS PATIENT INFORMATION LEAFLET
PRODUCED AUGUST 2005
UPDATED MAY 2010, MAY 2013

REVIEW DATE MAY 2016